1. Field of the Invention
This invention relates to analog and digital processors and methods, and more particularly to preview mode low resolution output systems and methods for charge coupled devices (CCDs), CMOS imagers, and cameras.
2. Description of the Related Art
Camera systems using charge coupled devices (CCDs) and imagers of many kinds are well-known for capturing signals according to many different CCD output formats and pixel configurations. According to one such format, in order to obtain a still image with acceptable resolution and contrast from a CCD, a minimum of 10 bits of resolution is desired. To practically capture a CCD image, the data read-out time from the CCD is very limited. Accordingly, one such front end interface which accepts CCD data for conversion into digital form operates typically up to 16 MHz with a 10-bit analog-to-digital converter. A camera using this front-end can produce a digital still image with up to 8 k×8 k pixels. The feature set available in known CCD camera systems is increasing to include more functionality, as well as extended dynamic range. Such extended functionality comes at a price in terms of electronic complexity and power consumption. For example, some current camera systems include a liquid crystal display (LCD) screen to enable viewing of images in a real-time viewfinder. This requires the CCD and associated processing chips to run in a video mode and to remain powered up while the screen is in use. This can dissipate a large amount of power that tends to shorten battery life. In such an operational mode, front end circuitry is operated at a resolution level which is unnecessary for driving the relatively low resolution LCD display, thereby consuming power needlessly.
Accordingly, there is a need to enable low power operation of the analog and digital subsystems in CCD camera and imager systems that convert analog data into digital signal forms for user applications. It is desirable to achieve lower power even at a sacrifice in resolution in the front end system.